It is known that various technologies are used in the ceramics sector to manufacture ceramic articles such as tiles and the like and can be distinguished substantially according to the forming method that they use.
Forming by pressing is known, for example, and generally provides for the wet milling of the raw materials in drum mills in order to obtain an aqueous suspension of milled solid particles that is conventionally known as slurry.
The resulting slurry is discharged from the mill and deposited in dedicated tanks, which are provided with means for moving said slurry and in which, in the case of the manufacture of porcelain stoneware articles, it is possible to add appropriately milled coloring oxides in order to obtain slurries having various colors.
The slurry is then dried inside spray driers in order to obtain powders that have a controlled degree of humidity, which are fed toward the article forming presses after a settling and homogenization step.
As an alternative, it is also known to form articles by extrusion; this method uses slurries that are first filtered within appropriately provided filter presses in order to obtain a plastic paste.
Said plastic paste is then extruded through dies, from which it exits as a continuous strand to be cut into articles having the chosen dimensions.
Regardless of whether forming has occurred by pressing or by extrusion, the resulting articles are fired in a kiln, after optional surface decoration and/or glazing.
However, these known methods are not free from drawbacks, including the fact that the slurries discharged from the mills must be subjected to an intermediate treatment (drying or filtering) performed before forming the articles, and said treatment requires the availability of dedicated equipment and entails structural complications of the production facilities, an increase in the installation and running costs of said facilities, an increased length and reduced speed of production lines, and an increase in labor costs and energy consumption.
Moreover, particularly in the case of forming porcelain stoneware articles by pressing, managing powders in different colors, formats and/or particle sizes is rather complicated and expensive.
To obviate these drawbacks, a method for forming ceramic articles is also known which essentially consists in depositing in succession on a porous working surface a plurality of uniform layers of a fluid mixture of ceramic material, each layer being deposited on the previous one after drying the latter by heating it.
In particular, the drying step consists in transferring heat by convection and/or radiation to the intermediate component being produced, so as to achieve evaporation of the moisture contained in the freshly deposited layer.
However, even this known method is susceptible of further improvements aimed in particular at reducing the operating temperatures, in order to avoid the formation of defects in the resulting articles caused by expansion of air microbubbles retained in the deposited layers and/or by the boiling of the water contained inside the intermediate components being processed, and to contain energy consumption.